1 : Charles Goodyear once accidentally P : and found that the resulting rubber Q : dropped a mixture of natural rubber R : was harder, stronger, more elastic S : and sulphur over a hot stove 6 : and non-sticky The Proper sequence should be:

The correct answer is A. PSQR.

Here is a brief explanation of each option:

• Option A: PSQR. This is the correct sequence. Charles Goodyear accidentally dropped a mixture of natural rubber and sulphur over a hot stove, and found that the resulting rubber was harder, stronger, more elastic, and non-sticky.
• Option B: QSPR. This is not the correct sequence. According to the question, Charles Goodyear accidentally dropped a mixture of natural rubber and sulphur over a hot stove. This means that Q (dropped a mixture of natural rubber and sulphur) must come before R (over a hot stove).
• Option C: RSQP. This is not the correct sequence. According to the question, Charles Goodyear accidentally dropped a mixture of natural rubber and sulphur over a hot stove. This means that R (over a hot stove) must come after Q (dropped a mixture of natural rubber and sulphur).
• Option D: SQPR. This is not the correct sequence. According to the question, Charles Goodyear accidentally dropped a mixture of natural rubber and sulphur over a hot stove. This means that S (and sulphur) must come after Q (dropped a mixture of natural rubber).